Cleaning composition and method for removing residues

ABSTRACT

Non-corrosive cleaning compositions that are aqueous based and useful for removing photoresist, plasma etch and CMP residues from a substrate. One preferred cleaning composition comprises: (i) a hydroxylamine or a hydroxylamine salt compound;(ii) at least one fluorine-containing compound; and (iii) water. Another cleaning composition comprises: (i) a compound selected from the group consisting of: an amine, a quatenary ammonium hydroxide, and ammonium hydroxide; (ii) at least one fluorine-containing compound; and (iii) water.

This is a Continuation-In-Part of U.S. patent application Ser. No.08/709,053, filed Sep. 6, 1996.

BACKGROUND OF THE INVENTION

1. Field of The Invention

This invention relates to a cleaning composition and method for use inmicroelectronics manufacturing, and more particularly to a non-corrosivecleaning composition and method for removing photoresist, plasma etchand chemical-mechanical polishing (CMP) residues on substrates.

2. Description of Art

In the manufacture of microcircuits, positive photoresists are used asan intermediate mask for transferring an original mask pattern of areticule onto wafer substrates by means of a series of photolithographyand plasma etching steps. One of the steps in the microcircuitmanufacturing process is the removal of the patterned photoresist filmsfrom the substrates. In general, this step is affected by one of twomethods. One method involves a wet stripping step in which thephotoresist-covered substrate is brought into contact with a photoresiststripper solution that consists primarily of an organic solvent and anamine. However, stripper solutions cannot completely and reliably removethe photoresist films, especially if the photoresist films have beenexposed to UV radiation and plasma treatments during fabrication. Somephotoresist films become highly cross-linked by such treatments and aremore difficult to dissolve in the stripper solution. In addition, thechemicals used in these conventional wet stripping methods are sometimesineffective for removing inorganic residual materials formed during theplasma etching of metal or oxide layers with halogen-containing gases.

An alternative method of removing a photoresist film involves exposing aphotoresist-coated wafer to oxygen plasma in order to burn the resistfilm from the substrate surface in a process known as oxygen plasmaashing. Oxygen plasma ashing has become more popular in the microcircuitmanufacturing process because it is carried out in a vacuum chamber and,hence, is expected to be less susceptible to airborne particulate ormetallic contamination. However, oxygen plasma ashing is also not fullyeffective in removing plasma etching residues noted above. Instead,removal of these plasma etching residues must be accomplished bysubsequently exposing the photoresist film to certain alkalinesolutions. Several commercial products are now available to clean theplasma etching residues left by plasma etching followed by oxygenashing. For example, EKC 265, available from EKC Technology, Inc., is aplasma etching cleaning solution composed of water, alkanolamine,catechol and hydroxylamine. Such a composition is disclosed in U.S. Pat.No. 5,279,771 to Lee. ACT 935, available from Ashland Chemical, isanother plasma etching cleaning solution and is composed of water,alkanolamine and hydroxylamine. In both cases, hydroxylamine is used asa corrosion inhibitor. R-10, a post-strip rinse available fromMitsubishi Gas Chemical, is composed of water, alkanolamine and a sugaralcohol, wherein the sugar alcohol acts as a corrosion inhibitor.

Although these commercial products can effectively dissolve plasmaetching residues, the combination of water and alkanolamine containedtherein can also attack the metallic layers deposited patternwise on thesubstrate. The addition of a corrosion inhibitor to these products canmitigate to a certain extent, the unwanted attack on the metallic layersand oxide layers deposited on the substrate. However, since theseproducts have a pH above 11, even in the presence of a corrosioninhibitor, they may attack certain corrosion-sensitive metal layers.Particularly, metal layers such as aluminum or aluminum alloys (e.g.,Al-Cu-Si), titanium nitride, titanium tungsten and the like areparticularly corrosion sensitive. Furthermore, while the addition of asuitable corrosion inhibitor is essential to prevent corrosion of thesubstrate metal layers, the corrosion inhibitor must not inhibit theremoval of the plasma etching residue.

It is difficult to balance effective plasma etching residue removal andcorrosion inhibition because chemical compositions of the plasma etchingresidues are generally similar to those of the metal layers or oxidelayers on the substrate. The alkanolamine used in the prior art cleaningcompositions was oftentimes found to attack both the plasma etchingresidue and the substrate metal layers. Moreover, if a post-cleanerrinse such as isopropyl alcohol was not used, the corrosion could bevery severe. In addition, some types of the corrosion inhibitors havebeen found to retard plasma etching residue removal. There has alsoalways been a tradeoff between speed of plasma etching residue removaland substrate metal layer corrosion inhibition. Accordingly, there hasremained a need for a method of quickly and effectively removing theplasma etching residues without causing metal layer corrosion.

Several other patents in the photoresist stripper/cleaner applicationfield exist as follows, although none of them disclose the use of themethod or compositions of the present invention:

Japanese Patent Application No. 7-028254, assigned to Kanto Kagaku,discloses a non-corrosive resist removal liquid comprising a sugaralcohol, an alcohol amine, water, and a quaternary ammonium hydroxide.

PCT Published Patent Application No. WO 88-05813 teaches a positive ornegative photoresist stripper containing butyrolactone or caprolactone,quaternary ammonium hydroxide compound, and optionally, a nonionicsurfactant.

U.S. Pat. No. 4,239,661 to Muraoka et al. discloses a surface-treatingagent comprising an aqueous solution of 0.01% to 20% trialkyl(hydroxyalkyl) ammonium hydroxide. This agent is useful in removingorganic and inorganic contaminants deposited on the surface ofintermediate semiconductor products.

U.S. Pat. No. 4,904,571 to Miyashita et al. teaches printed circuitboard photoresist stripper composition containing a solvent (e.g.,water, alcohols, ethers, ketones, and the like), an alkaline compounddissolved in the solvent, including quaternary ammonium hydroxide, and aborohydride compound dissolved in the solvent.

U.S. Pat. No. 5,091,103 to Dean et al. teaches a positive photoresiststripping composition containing: (A) N-alkyl-2-pyrrolidone; (B)1,2-propanediol; and (C) tetraalkylammonium hydroxide.

U.S. Pat. No. 5,139,607 to Ward et al. teaches positive and negativephotoresist stripping composition containing: (A) tetrahydrofurfurylalcohol; (B) a polyhydric alcohol (e.g., ethylene glycol or propyleneglycol); (C) the reaction product of furfuryl alcohol and an alkyleneoxide; (D) a water-soluble Bronstead base type hydroxide compound (e.g.,alkali metal hydroxide, ammonium hydroxide and tetramethyl ammoniumhydroxide); and (E) water. Optionally, the composition may also containup to 1% of a nonionic surfactant.

U.S. Pat. No. 5,174,816 to Aoyama et al. discloses a composition forremoving chlorine remaining on the surface of an aluminum line patternsubstrate after dry etching, which composition comprises an aqueoussolution containing 0.01 to 15% by weight of a quaternary ammoniumhydroxide, such as trimethyl (2-hydroxyethyl) ammonium hydroxide, and0.1 to 20% by weight of sugar or sugar alcohol, such as xylitol,mannose, glucose and the like.

In addition to photoresist and plasma etch removal, another step that iswidely used in the manufacturing of microcircuits includes aplanarization process such as planarization etch back orchemical-mechanical polishing (CMP). A planarization process is neededin microcircuit manufacturing because the deposition of successivelayers of materials on the substrate causes the surface to becomesuneven and it is difficult to lithographically print images over theuneven topography. The planarization process evens the surface making iteasier to form an image thereon by lithographic printing.

In planarization etch back, a planarizing material, such as a polymerresist or a spin on glass (SOG) containing SiO₂ is typically spun on theuneven topography to planarize the substrate. The substrate is thensubjected to a plasma etch process wherein the planarizing material andunderlying substrate are etched at approximately the same rate to form aplanar surface. With this process, the plasma etch residues and portionsof the planarizing material typically remain on the substrate and mustbe removed.

In the CMP process, the surface that is to be planarized is brought intocontact with a rotating polishing pad in the presence of an abrasiveslurry. A portion of the surface layer of the substrate is removed bythe chemical nature of the slurry and the abrasive action of thepolishing pad. The problem with CW is that residues are left behind onthe substrate, either from the slurry that is used in the CMP process orfrom detached substrate material. These residues can contaminate thevias, and deleteriously affect the workings of the microcircuit.Especially severe contaminants to microcircuits are residues from thepolishing slurry which contain metal contaminants including alkalinemetals such as sodium, potassium, and the like, and iron.

The CMP contaminates are typically removed from the substrate surface bycontacting the surface with a caustic solution containing ammoniumhydroxide or ammonium hydroxide mixed with hydrogen peroxide. Inaddition, brush scrubbing with these solutions has also been used toremove particulate matter. However, these caustic solutions can diffusethrough defects in the substrate and attack the metal layers such asaluminum, aluminum alloys, refractory metals, and the like. The metalattack may subsequently cause voids in the metal that can lead tofailure of the microcircuit.

Several patents describe attempts of solving the problem of metal attackusing the combination of a specific organic corrosion inhibitors and afluorine-containing compound. For example, U.S. Pat. No. 5,478,4436 toWinebarger et al, uses a combination of an organic corrosion inhibitor(glycol and dimethylsulfoxide) and fluorine-containing compounds such asammonium fluoride, hydrogen fluoride and perfluoric acid. U.S. Pat. No.5,320,709 to Bowden et. al. discloses the use of an anhydrous ammoniumfluoride salt in polyhydric alcohol. The problem with these compositionsis that organic solvents are only weak corrosion inhibitors, and a highconcentration of organic solvent (greater than 50% by weight) isrequired. Thus, there is a problem with waste removal since theorganic-based cleaning solution is environmentally unfriendly.

Therefore, there remains a need for a composition that removesphotoresist, plasma etch, and CMP residues from substrates.Additionally, there remains a need for such a composition that does notdeleteriously affect the substrate. Further, there remains a need forsuch a composition that is aqueous-based so that the disposal thereofwill not harm the environment.

SUMMARY OF THE INVENTION

The present invention is, in brief summary, directed to a non-corrosivecleaning composition that is aqueous based and useful for removingphotoresist, plasma etch and CMP residues from a substrate. Thecomposition comprises:

(i) a hydroxylamine or a hydroxylamine salt compound;

(ii) at least one fluorine-containing compound; and

(iii) water.

In an alternative embodiment, this invention contemplates a cleaningcomposition comprising:

(i) a compound selected from the group consisting of an amine, aquaternary ammonium hydroxide and ammonium hydroxide;

(ii) at least one fluorine-containing compound; and

(iii) water.

The invention further contemplates a method of removing residues from asubstrate comprising the steps of

contacting a substrate containing residues with at least one of theabove mentioned cleaning compositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A non-corrosive cleaning composition that is useful for removingphotoresist, plasma etch and CMP residues from a substrate. Thecomposition preferably comprises:

(i) a hydroxylamine or a hydroxylamine salt compound;

(ii) at least one fluorine-containing compound; and

(iii) water.

The composition can contain either hydroxylamine or a salt of thehydroxylamine produced by reacting the hydroxylamine with an acid, e.g.,nitric acid or sulfuric acid. Preferred hydroxylamine salts that can beused to form the cleaning composition of the present invention includehydroxylammonium nitrate (also referred to as HAN), hydroxylammoniumsulfate (also referred to as HAS), hydroxylammonium phosphate,hydroxylammoniun chloride, hydroxylammonium oxalate, hydroxylammoniumcitrate, and the like. Alkyl-substituted derivatives of hydroxylammoniumsalts are also useful; e.g., hydroxyl diethylammonium salts and thelike.

The fluorine-containing compound in the above composition can beselected from acid fluorides, fluorinated salts, polyammonium fluoridesalts and mixtures thereof Preferred acid fluorides include hydrogenfluoride, (HF), and perfluoric acid. Preferred fluoride salts areammonium fluoride, ammonium bifluoride, ammonium difluoride andtetraalkyl ammonium fluoride salts such as tetramethyl ammonium fluorideand tetraethyl ammonium fluoride. Preferably, the fluorine-containingcompound will comprise about 0.5 to 10 wt. % based upon the weight ofthe composition

The polyammonium salts may be prepared by reacting a polyamine with HFto form the polyammonium fluoride salt. For example, HF may be reactedwith an aqueous solution of ethylene diamine to form anethylenediammonium difluoride. Alternatively, an excess amount of HF maybe reacted with the polyamine to form the polyammonium salt. Preferredpolyammonium salts include ethylenediammonium difluoride anddiethylenetriammonium trifluoride.

It is believed that the fluorine-containing compound aids in removal ofcontaminates by slightly etching the underlying silicon-based substrateso that any contaminates on the surface or embedded in the substrate areremoved. Also, it is believed that many of the plasma etch residues,especially those containing fluoride species, are soluble in fluorinesolutions and will also be removed. Hydroxylamines and salts thereof actas corrosion inhibitors and aid in the removal of residues. Thus, thecombination of a fluorine compound and a hydroxylamine or hydroxylaminesalt has been found by the present applicants to be particularly usefulas a cleaning composition.

The pH of the cleaning composition preferably ranges from weakly acidicto slightly basic so as to not attack or corrode the metal used in themicrocircuit fabrication. If the cleaning composition is either toocaustic or too acidic, the metal layers on the substrate are subject toattack. Therefore, the components in the cleaning composition should beadmixed in appropriate concentrations to provide a composition having apH with a preferred range from about 2 to 9, and more preferably fromabout 2 to 6.

In a preferred embodiment of this invention, the fluorine-containingcompound is admixed with a composition comprising water, a hydroxylaminesalt and at least one basic compound selected from the group consistingof: amines, quaternary ammonium hydroxides and ammonium hydroxide. Suchcompositions are described in copending U.S. patent application Ser. No.08/709,053, filed Sep. 6, 1996, the subject matter of which isincorporated herein by reference.

Amines that may be used as a component in the cleaning compositionsinclude alkanolamines such as monoethanolamine, diethanolamine,triethanolamine, diethylene-glycolamine, N-hydroxylethylpiperazine, andthe like. Quaternary ammonium hydroxides that can be used in thecompositions include tetraalkylammonium hydroxides having methyl, ethyl,propyl, butyl, hydroxyethyl, and the combinations thereof (e.g.,tetramethylammonium hydroxide (hereinafter referred to as TMAH),tetraethyl-ammonium hydroxide, trimethyl hydroxyethylammonium hydroxide,methyl tri (hydroxyethyl) ammonium hydroxide, tetra (hydroxyethyl)ammonium hydroxide, benzyl trimethylammonium hydroxide and the like).Additionally, a combination of ammonium hydroxide with one or morequaternary ammonium hydroxides may also be used. Preferably, thehydroxylamine salt will comprise about 1% to 70% by weight, the basecompound will comprise about 0.1% to 10% by weight, and water willcomprise the remainder of the composition, these weight percentagesbeing based on the total combined weight of hydroxylamine salt, basiccompound and water (excluding the weight of the fluorine-containingcompounds and other optional components of the cleaning composition).

A chelating stabilizer may be optionally included in the cleaningcomposition to stabilize the hydroxylamine salts. Suitable chelatingstabilizers include triethylenetetramine (hereinafter referred to asTETA); 2,2'-[[methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol(Tradename is IRGAMET 42), (2-benzothiazolythio)succinic acid (Tradenameis IRGACOR 252), tricine, bicine, and other water-soluble chelatingcompounds. Preferably, the stabilizer is present in the composition ofthe invention in the range of about 5 ppm to about 5000 ppm by weightbased on the a total weight of cleaning composition.

A surfactant may also be optionally included in the cleaning compositionso as to enhance the power of the plasma etching residue removal fromthe substrate. Suitable surfactants are selected from nonionic types,cationic types and anionic types of surfactants. Preferably, asurfactant is present in the composition of the invention in the rangeof about 0.1 ppm to 100 ppm by weight to a total weight of the cleaningcomposition. The cleaning composition may also, optionally, contain aminor amount of a corrosion inhibitor such as sugar alcohols, catecholand the like.

Another optional agent that may be included in the cleaning compositionis a corrosion inhibitor. The preferred corrosion inhibitors are lacticacid, salicyl alcohol, salicyl aldoxime, gallic acid, gallic acid estersand alizarin.

This invention also contemplates a cleaning composition comprising:

(i) at least one compound selected from the group consisting of: anamine, a quaternary ammonium hydroxide, and ammonium hydroxide;

(ii) at least one fluorine-containing compound; and

(iii) water.

The quaternary ammonium hydroxide and fluorine-containing compounds arethe same as those described previously in this invention. It is believedthat the quatenary ammonium hydroxides are used to remove photoresistresidues; while the fluorinecontaining compound solubilizesfluorine-containing plasma etch residues and slightly etches thesubstrate to remove particles on the surface and embedded in thesubstrate. Other components may also be added in the cleaningcomposition such as chelating agents, surfactants and corrosioninhibitors as were previously described above.

The pH of the above cleaning composition may range anywhere from weaklyacidic to slightly basic so as to not attack or corrode the metal usedin the microcircuit fabrication. Therefore, the components in thecleaning composition should be admixed in appropriate concentrations tomaintain the pH range from about 2 to 9.

This invention further contemplates the method of removing residues froma substrate comprising the steps of:

applying one of the above mentioned cleaning solutions to the substratecontaining residues.

The cleaning method of the present invention can also be used incombination with a dry stripping process if photoresist or other polymerresidues remain on the surface. Dry stripping is typically conductedprior to the present cleaning method. Any suitable dry stripping processcan be used including O₂ plasma ashing, ozone gas phase-treatment,fluorine plasma treatment, hot H₂ gas treatment (described in U.S. Pat.No. 5,691,117), and the like. The preferred dry stripping process is O₂plasma ashing.

Furthermore, the cleaning method can also be used in combination withozonated water which is used to strip off photoresist and otherresidues. The ozonated water can be a simple mixture of ozone andultra-pure water, e.g., DI water. The ozone can be generated by anyconventional means, e.g., an ozone generator. The mixing of the ozoneand water may be achieved by any suitable method, such as jetting theozone into the water by a gas feed nozzle; feeding the water and ozoneinto a spiral mixer; aspirating the gas into the flow of water; andfeeding the ozone into a treatment tank regulated at a given pressure sothat ozone is dissolved into the water. The ozonated water can then becontacted with the substrate by any suitable method such as placing theozonated water into a tank and submerging the substrates into theozonated water, or by use of a spray rinse.

While the invention has been described above with reference to specificembodiments thereof, it is apparent that many changes, modifications andvariations can be made without departing from the inventive conceptdisclosed herein. Accordingly, it is intended to embrace all suchchanges, modifications and variations that fall within the spirit andbroad scope of the appended claims. All patent applications, patents andother publications cited herein are incorporated by reference in theirentirety.

What is claimed is:
 1. A cleaning composition comprising:(i) ahydroxylamine salt compound selected from the group consistiong ofhydroxylammonium nitrate, hydroxylammonium phosphate, hydroxylammoniumoxalate, hydroxylammonium citrate, and hydroxylammonium chloride; (ii)at least one flourine-containing compound; and (iii) water.
 2. Thecomposition of claim 1 wherein said fluorine-containing compound is atleast one compound selected from the group consisting of:a) an acidfluoride; b) a fluorinated salt; and c) a polyammonium fluoride salt. 3.The composition of claim 1 wherein said fluorine-containing compound isat least one compound selected from the group consisting of: hydrogenfluoride, perfluoric acid, ammonium fluoride, tetramethylammoniumfluoride, ammonium bifluoride, ethylenediammonium difluoride anddiethylenetriammonium trifluoride.
 4. The composition of claim 1 furthercomprising at least one additional component selected from the groupconsisting of: an amine, a quaternay ammonium hydroxide and ammoniumhydroxide.
 5. The composition of claims 5 wherein said quaternaryammonium hydroxide compound is selected from the group consisting of:tetamethylammonium hydroxide, tetaethylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, methyl tri (hydroxyethyl) ammoniumhydroxide, and tetra(hydroxyethyl)ammonium hydroxide.
 6. The compositionof claim 3 wherein said amine is selected from the group consisting of:monoethanolamine, diethanolamine, triethanolamine, diethyleneglycolamine, and N-hydroxyethylpiperazine.
 7. The composition of claim 1further comprising a corrosion inhibitor.
 8. The composition of claim 7wherein said corrosion inhibitor is selected from the group consistingof: lactic acid, salicyl alcohol, salicyl aldoxime, gallic acid, gallicacid esters, and alizarin.
 9. The composition of claim 1 furthercomprising a surfactant.
 10. The composition of claim 1 furthercomprising a chelating agent.
 11. The composition of claim 1 where thepH is within a range between about 2 to
 6. 12. A cleaning compositioncomprising:(i) a compound selected from the group consisting of:trimethyl hydroxyethylammonium hydroxide, methyl tri (hydroxyethyl)ammonium hydroxide, tetra(hydroxyethyl)ammonium hydroxide, diethyleneglycolamine, and N-hydroxyethylpiperazine; (ii) at least onefluorine-containing compound; and (iii) water.
 13. The composition ofclaim 12 wherein said fluorine-containing compound is selected from thegroup consisting of:a) an acid fluoride; b) a fluorinated salt; and c) apolyammonium fluoride salt.
 14. The composition of claim 12 wherein thefluorine-containing compound is selected from the group consisting of:hydrogen fluoride, perfluoric acid, ammonium fluoride,tetramethylammonium fluoride, ammonium bifluoride, ethylenediammoniumdifluoride and diethylenetriammonium trifluoride.
 15. The composition ofclaim 12 further comprising of a corrosion inhibitor.
 16. Thecomposition of claim 15 wherein said corrosion inhibitor is selectedfrom the group consisting of: lactic acid, salicyl alcohol, salicylaldoxime, gallic acid, gallic acid esters, and alizarin.
 17. Thecomposition of claim 12 further comprising a surfactant.
 18. Thecomposition of claim 12 further comprising a chelating agent.
 19. Thecomposition of claim 12 where the pH ranges is within a range betweenabout 2 to 9.